Stahl Stefan W, Puchner Elias M, Gaub Hermann E
Chair for Applied Physics and Center for NanoScience, Ludwig-Maximilians-University, Amalienstr. 54, Munich D-80799, Germany.
Rev Sci Instrum. 2009 Jul;80(7):073702. doi: 10.1063/1.3157466.
Photothermal cantilever excitation provides a fast and easy to implement means to control the deflection of standard atomic force microscopy cantilevers. Minute heat pulses yield deflections on the order of several tens of nanometers or when the deflection is kept constant, forces of several hundreds of piconewton can be applied. In our case these pulses resulted in less than 1 K temperature changes at the sample position. Here we present and characterize the implementation of photothermal actuation for single-molecule force-spectroscopy experiments. When molecules are stretched under force-clamp conditions, fast control cycles that re-establish the pulling force after the rupture of molecular domains are essential for detecting the complete unfolding pattern with high precision. By combining the fast response of photothermal cantilever excitation with a conventional piezoactuator, a fast force-clamp with high accuracy and large working distances is reached. Simple feedback mechanisms and standard cantilever geometries lead to step response times of less than 90 micros, which is more than one order of magnitude faster than those of conventional force-clamp systems that are based only on piezo feedback. We demonstrate the fast and accurate performance of the setup by unfolding a protein construct consisting of one green fluorescent protein and eight surrounding immunoglobulin domains at constant force.
光热悬臂梁激发提供了一种快速且易于实现的方法来控制标准原子力显微镜悬臂梁的偏转。微小的热脉冲会产生几十纳米量级的偏转，或者当偏转保持恒定时，可以施加几百皮牛顿的力。在我们的实验中，这些脉冲在样品位置引起的温度变化小于1K。在此，我们展示并描述了用于单分子力谱实验的光热驱动的实现。当分子在力钳条件下被拉伸时，在分子域破裂后重新建立拉力的快速控制周期对于高精度检测完整的解折叠模式至关重要。通过将光热悬臂梁激发的快速响应与传统压电致动器相结合，可实现具有高精度和大工作距离的快速力钳。简单的反馈机制和标准的悬臂梁几何形状导致阶跃响应时间小于90微秒，这比仅基于压电反馈的传统力钳系统快一个多数量级。我们通过在恒定力下展开由一个绿色荧光蛋白和八个周围免疫球蛋白结构域组成的蛋白质构建体，展示了该装置的快速和准确性能。
